From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51540) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XlH1M-0000Aq-M5 for qemu-devel@nongnu.org; Mon, 03 Nov 2014 07:46:13 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XlH1H-00005U-RM for qemu-devel@nongnu.org; Mon, 03 Nov 2014 07:46:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54176) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XlH1H-00005Q-Ja for qemu-devel@nongnu.org; Mon, 03 Nov 2014 07:46:03 -0500 Date: Mon, 3 Nov 2014 14:45:54 +0200 From: "Michael S. Tsirkin" Message-ID: <1415018633-16041-23-git-send-email-mst@redhat.com> References: <1415018633-16041-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1415018633-16041-1-git-send-email-mst@redhat.com> Subject: [Qemu-devel] [PULL 22/29] hw/virtio/vring/event_idx: fix the vring_avail_event error List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Peter Maydell , Stefan Hajnoczi , Bin Wu , Anthony Liguori From: Bin Wu The event idx in virtio is an effective way to reduce the number of interrupts and exits of the guest. When the guest puts an request into the virtio ring, it doesn't exit immediately to inform the backend. Instead, the guest checks the "avail" event idx to determine the notification. In virtqueue_pop, when a request is poped, the current avail event idx should be set to the number of vq->last_avail_idx. Signed-off-by: Bin Wu Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Stefan Hajnoczi --- hw/virtio/dataplane/vring.c | 8 ++++---- hw/virtio/virtio.c | 2 +- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c index 372706a..61f6d83 100644 --- a/hw/virtio/dataplane/vring.c +++ b/hw/virtio/dataplane/vring.c @@ -352,10 +352,6 @@ int vring_pop(VirtIODevice *vdev, Vring *vring, goto out; } - if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) { - vring_avail_event(&vring->vr) = vring->vr.avail->idx; - } - i = head; do { if (unlikely(i >= num)) { @@ -392,6 +388,10 @@ int vring_pop(VirtIODevice *vdev, Vring *vring, /* On success, increment avail index. */ vring->last_avail_idx++; + if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) { + vring_avail_event(&vring->vr) = vring->last_avail_idx; + } + return head; out: diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 2c236bf..013979a 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -469,7 +469,7 @@ int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem) i = head = virtqueue_get_head(vq, vq->last_avail_idx++); if (vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) { - vring_avail_event(vq, vring_avail_idx(vq)); + vring_avail_event(vq, vq->last_avail_idx); } if (vring_desc_flags(vdev, desc_pa, i) & VRING_DESC_F_INDIRECT) { -- MST